The present invention relates to a data recording medium typified by a digital versatile disk (DVD) or a high-density optical disk which permits high-density recording of data, such as images and sound, as well as to a data reproducing apparatus for reproducing data from the data recording medium.
So-called laser disks (LD) and compact disks (CDs) have already become widespread as optical disk having data, such as videos and sound, recorded thereon. However, the laser disk is unable to offer the viewer a choice among alternatives relating to videos or audio to be reproduced. In short, the laser disk has been unable to realize a variety of interactive reproduce patterns. For example, when a foreign-language movie recorded on an LD is reproduced, the viewer is not allowed to select whether to display Japanese subtitles or English subtitles on the screen or whether to reproduce the sound dubbed in English or the sound dubbed in Japanese.
In contrast to the case of the CD, various proposals or developments have recently been made with regard to a digital video disk or digital versatile disk (DVD), which is equal in size to an optical disk but has about ten times the storage capacity. So long as subtitles in a plurality of languages and sound dubbed in a plurality of languages are recorded on the DVD together with reproduce control data, the viewer can make a choice from alternatives, thus enabling a variety of interactive reproduce patterns.
The DVD has large storage capacity and enables simultaneous recording of sound and video data sets, as well as recording of solely video data or solely sound data. To realize a variety of interactive manners for reproducing video and sound data (both of which will be hereinafter referred to as “substantial data”), reproduce control information representing the procedures by which the substantial data are reproduced is also recorded on the DVD.
The reproduce control information is recorded on a disk so as to constitute a hierarchical structure in order to fulfill diverse functions by use of a simpler structure. The reproduce control information is recorded so as to be spread out over the disk in units, each unit including a set of substantial information items. The interactive characteristics of the DVD video format enable fulfillment of a great number of functions, thereby providing the user with a variety of reproduce patterns. For these reasons, the information for controlling reproduce of a DVD video must inevitably become complicated. The reproduce control information is prepared on premise that an information reproducing apparatus can fulfil all the available reproduce patterns (or functions).
However, for example, when an attempt is made to reproduce only sound data included in the video data recorded on the DVD, by use of a sound-reproduce-only DVD player (for instance, only sound data are reproduced from a DVD on which a live performance of a certain singer is recorded), the reproduce control information includes many information items that are unnecessary for reproducing sound data. Since the sound-reproduce-only DVD player is not required to reproduce video data, the reproduce control information items, such as subtitles or multi-angles, required for interactive reproduce of videos are unnecessary.
Even in the case of the sound-reproduce-only DVD player, various information items are available as reproduce control information for reproducing only audio information in various manners. Of the sound-only DVD players, an unsophisticated player which plays back linear PCM sound data in the form of two-channel stereo sound must select from the sound data reproduce control information only the information items required for reproducing two-channel stereo sound.
The reproduce control information and the substantial data are spread over the DVD disk. If an attempt is made to ascertain the total time required for reproducing the entire DVD disk, the reproduce control information items recorded so as to become spread over the disk must be aggregated. In the hierarchical structure in which the reproduce control information is recorded so as to become spread over the disk in order to readily fulfill complicated functions by use of a simple structure, ascertainment of the information about the overall disk in a single operation contrarily involves more complicated processing.